Japanese Patent Application No. 2001-19039, filed Jan. 26, 2001, is hereby incorporated by reference in its entirety.
The present invention relates to manufacture of semiconductor devices, and more particularly to an improvement of a target jig in a sputtering apparatus that is used to form thin films of semiconductor integrated circuits.
When gas for discharge such as argon is injected in a vacuum space and a voltage is applied to an electrode, a glow discharge (plasma) is generated. In this instance, ions in the plasma collide with a cathode target and strike out target atoms (i.e., a sputtering phenomenon takes place). A sputtering apparatus uses this sputtering phenomenon to form a thin film on a substrate.
Among the sputtering apparatuses, a magnetron sputtering apparatus that performs sputtering by a magnetron discharge using magnetic fields to increase the plasma density is known. Magnetron sputtering provides an ideal discharge characteristic at a low voltage with a large current, and therefore has a good sputtering efficiency and is capable of forming films at a high speed. Also, since electrons are captured in the vicinity of the target, collision of electrons with a substrate is reduced and an elevation in the temperature of the substrate is suppressed such that films can be formed at low temperatures.
As it is well known, a magnetron sputtering is structured in a manner that a magnet is attached to a back of a target such that a part of lines of magnetic force becomes parallel with a cathode surface. Generally, it is equipped with a backing plate (a copper plate for cooling) that is connected to a target and a copper plate (connected to an electrode) that is provided for enclosing a magnet and conducting cooling water.
It is noted that the target that is connected to the backing plate has a side portion that can be held by a ring-shape jig (a target jig). The target jig is disposed on the backing plate around the target, and also functions as a jig that covers the side portion of the target and the backing plate to prevent particles from adhering thereto. The target jig is formed from stainless steel or aluminum, titanium or the like that hardly affects the sputtering process.
There are cases when an abnormal discharge such as a micro-arc is generated in a narrow gap between the target jig and the vacuum container. As a result, the plasma state not only becomes unstable due to a rapid fall of a discharge voltage near an outer periphery of the target, but also the target material may be removed and cause contamination with particles.
The present invention has been made in view of the circumstances described above, and it is an objective to provide a sputtering apparatus that has a target jig that can suppress abnormal discharges such as micro arcs.
The present invention relates to a sputtering apparatus in which gas for discharge is injected in a vacuum container and a high-frequency glow discharge is generated therein to collide ions in plasma with a cathode target to thereby generate particles to a substrate, the sputtering apparatus comprising a target jig that is provided to hold a side portion of the target, wherein each of surfaces of the target jig and the vacuum container that closely faces each other is finished with mirror.
In the sputtering apparatus in accordance with the present invention, the surfaces of the target jig and the vacuum container that are facing each other are finished with mirror so that the generation of micro-arcs is suppressed.
As a result, this can provide a sputtering apparatus having a target jig that can suppress abnormal discharges such as micro-arcs and achieving generation of stable plasma.
As an uppermost surface layer, a thin oxide film may be coated on the mirror finished surface of the target jig, which is closely facing to the vacuum container. This maintains the mirror surface and protects the surface of the target jig that is exposed to the plasma.
The vacuum container may include a projected portion which protects the target jig from ions in the plasma.